Many different types of bone deformities can be corrected using external fixation systems. Such systems generally use rings, fixation plates, threaded rods or struts for manipulation, angulation, and translation of the bone deformities.
Existing fixation systems on the market have many components thereof that are static and do not allow for certain adjustment and/or pivoting. Lack of flexibility in a fixation system may restrict attachment to certain bone areas at certain angles as well as restrict motion of the portion of the body that the external fixation system is being attached to in order to correct. Because of such lack of flexibility, such systems may make it more difficult for the physician to achieve an optimal clinical outcome.
External fixation devices have been used to stabilize, distract and compress bone fragments of long bones such as the tibia and femur, for example. There also exists a need to manipulate the positions of couplings connected to rods of such external fixation devices. For instance, a first rod of an external fixation device may be coupled to a first bone fragment via a first cross-pin connected to the first rod by a coupling mechanism while a second rod may be coupled to a second bone fragment via a second cross-pin connected to the second rod by another coupling mechanism. Additional coupling mechanism may be used to connect the first and second rods. After such an external fixation system is connected to the bones that it is treating, the coupling mechanisms may have to be moved along their coupled positions on the rods in order to provide distraction and/or compression to the bones.
There exists a need for an integrated external fixation device that can be used to manipulate the positions of such coupling mechanisms. Access to actuating the integrated external fixation device would be easy as it is used to guide the movement of the coupling mechanism while load transfer occurs through the external fixation device.
It is known to use gears in external fixation systems to transmit torque applied to the gear to another component of the system. Conventional worm gears, for example, require the axis of the driving worm gear to be tangent or parallel to the driven gear. This limits the configuration of gear designs as well as the configuration of external fixation systems using these gears. Clutches or ratchets may be used to prevent backdrive; however, the addition of these devices increases the number of components needed to provide or restrict the motion of such gears.